There have heretofore been proposed, as an example of image recording apparatus, various exposure apparatus which employ a spatial light modulator such as a digital micromirror device (DMD) or the like for exposing a film to an image represented by a light beam that is modulated depending on image data. The DMD comprises a number of micromirrors disposed in a two-dimensional array on a semiconductor substrate of silicon or the like and having respective reflecting surfaces whose angles are changed depending on a control signal. An exposure head combined with the DMD is relatively moved in a scanning direction along an exposure surface to expose a desired area of the exposure surface to the image represented by the light beam.
Generally, the micromirrors of the DMD are arranged in rows and columns that extend perpendicularly to each other. The DMD may be inclined to the scanning direction to keep scanning lines closely spaced for higher resolution.
For example, Japanese Laid-Open Patent Publication No. 2001-500628 (PCT Application) discloses an illuminating system for guiding light to an auxiliary area (spatial light modulator) having a plurality of light valves, the auxiliary area being inclined to the projection onto scanning lines for increased resolution. The disclosed illuminating system increases the resolution in a direction perpendicular to the scanning direction. The resolution in the scanning direction is normally determined by the scanning speed and the modulating speed of the spatial light modulator, and can be increased by lowering the scanning speed or increasing the modulating speed of the spatial light modulator.